Machining 304 stainless

[rmt9000]

We are re-machining a v-groove in a 304 stainless roller approximately 10” in diameter. The rollers come from two different suppliers. The rollers from one supplier (technically a SUS 304, JIS spec) machine 'well'. The others, supplied by a local machine shop, are very difficult to re-machine. The same person does all the machining, hence speeds, feeds, tooling and set-up are all the same. The most important thing about it are that the sides of the groove are smooth. There really are no structural concerns. The faced surfaces of those that will be difficult have a very light wavy look to them. First, is there any way to make those easier to machine, either through choice of tooling or by heat-treatment (stress relieving or annealing)? Secondly, even though 304 stainless is spec'd, can there be that much difference within the grade between different mills? And is there any way to overcome this other than specifying, say, Ugima 304 or something like that. Also, kind of as an afterthought, which is easier to machine, 304 or 304L? Thank you in advance for any advice.

 

[kenvlach]

In this case, the high quality suppliers offer improved machining grades of the same overall 304 chemistry (don't mean using the crappy 303). They don't give a lot of details, maybe trace alloying to give a controlled microstructure. Carpenter calls their improved machineability version Project 70+:

http://www.cartech.com/product_lite...?leftn=sao_products&lefto=empty&lefti=sao_pl0

304L is slightly poorer than 304 in machineability.

 

[gerhardl]

Agree with kenflach. By getting (from the suppliers) or analysing (spark analyis) you will most likely find some small variation in the mix/presence of different metal composites from the two suppliers. (Could also be structural due to process, but most likely composition.)

Example: For European (German quality ) 1.4571 (SS316Ti) the slight titanium amount added is especially added not for strenght but for machineability.

A really good supplier or producer of material should be able to advice you about machineability details or special tool machining procedures.

You can of course get this also from other sources (machining tools suppliers), but not without detailed material composition available.

 

[wellman]

304L is low carbon. Usually this is replaced with nickel or chromium instead of carbon. It can make a big differnece in the machinabilty. I would stay with 304 wherever possible.